A heterogeneous cellular network may be a cellular network including a macrocell and a femtocell. The heterogeneous cellular network may be realized by disposing a femtocell in an indoor region and a shadow region in the macrocell, thereby enhancing a terminal communication performance.
The femtocell may be classified into 1) a closed femtocell allowing access to only an authorized terminal and 2) an open femtocell allowing access to any terminal.
The closed femtocell may enhance a performance of the authorized terminal and robust to a security. Thus, the closed femtocell may be widely used for the heterogeneous cellular network.
In the closed femtocell, interference occurring between a macrocell and a femtocell may be an issue causing degradation in the performance of the femtocell. A number of methods may be used to solve this issue.
In one method, frequency resources of the macrocell and frequency resources of the femtocell may be allocated so as to be orthogonal to one another. The method may cause interference between the macrocell and the femtocell. However, a performance for each of the macrocell and the femtocell may be limited due to restrictions on a use of the frequency resources.
In another method, a portion of frequency resources may be allocated as shared frequency resources to be used by the macrocell and the femtocell, and remaining frequency resources may be allocated as exclusive frequency resources used by the macrocell or the femtocell. By using the method, one of the macrocell and the femtocell may not be allowed to use all frequency resources.
Accordingly, there is a desire for a method of enhancing a communication performance in the heterogeneous cellular network by avoiding interference between the macrocell and the femtocell while each of the macrocell and the femtocell is allowed to use the all frequency resources.